Recovery of sulphur from gases



Sept. 3o '1924. 1,510,342

N. E. RAMEUSH RECOVERY OF SULPHUR FROM GASES Filed Aug. 1o 192e www? Patented Sept. llt.,

NIELS E. RMBUSH, OF STOCKTON-O-TEES, ENGLAND.

iincovmwor sULrn-ua imola eases..

application md August 1o, 1920. serial ne. 462,690.'

To allfwhom lt may concern.:

. Be it known that I, NmLs EDwARn RAM- BUsH, a subject of the King of Denmark, re-

(Jrases, of which the following is a specification. v The wet process' of removing sulphur l from gases by passin .them through a suspension or sludge o iron -ox-ide or .other suitable oxide in water or a solution of a salt has certain advantages owing to the fact that the material may be pumped and tothe further fact that thorough contactl between .gas and liquid is more 4easily attained than between gas and solid.l Thus a circulatory process is more easily'realized when using a liquid than when using a solid,

since the liquid, 'which is a suspension from the:l rst or rapidly becomes a suspension, maybe' circulated through mixers continu'- ously traversed bythe gases and through one or more .vats applied with an injection `I have found that injecting air into an open vat is a very imperfect or costly mode of revivification, and that for satisfactory reviviication it is essential that the sulphided suspension should be brought indistributedcondition into contact with air or oxygen, for instance in thin layers such as are obtained in areaction tower.

When regard is had to`the recovery of the sulphurV as completely as possible, it is important that the contents of thel `f tank,

I vats or the like, containing the suspension or sludge which is being, rhas been, revivified, should not be in contact with the atmosphere, butin .direct contact with the gas with which they have been reacting.

My invention relates'to a process for re-` moving sulphur from gases, wherein a suspension or sludge of ferrie oxide or like oxide 1n water or a solution of a salt is action of air or oxygen. In the preferred method of carrying out the process the conditions are such that the" amount of reviviying gas esca ing from l the a paratus per unit of revivi cation et fecte is'the minimum 4practlcable. This is because the escaping reviviying g'as carries sulphur, so that if a larger volume of this .gas than is necessary be used the loss of sulphur may be of importance. siding in Stockton-on-Tees, England, have 5 linvented certain new and useful Improvements in the Recovery .of Sulphur froml This preferred method may be applied by circulating the revivifying gas in` a closed cycle through the'revivification apparatus, or Aby causing such a slow travel of the revivifying gas through the apparatus that the -partial pressure of the available oxygen ,in the gas is reduced to that be- A low which reviviication proceeds at an uneconomical rate.

comes reduced owing to the absorption of oxygen by the sulphided sludge and to dis- .y

solution vof the air in the liquid. Ora small proportion of fresh air may be periodically or continuously blown into one part of the system while an escapeis af- When air is used the content of'oxygen may readily be reduced'to 8 `per cent of the total volume of air used without rendering the process unec'onom-v .ica-l', and a considerably lower limit may be forded for `used airL at another part. Generally, however, 'it 1s Aessential to blow theexhausted air out of the system every now and then in orderto substitute fresh air.

Whether circulation of the reviviying gas be adapted or not, for satisfactory continuity of the process, a portion of the reviviiied suspension mayrbe withdrawn pe-,

riodically or continuously fromthe circu. lation and the precipitated sulphur separated from it by mechanical means (such as `fractional subsidence vor centrifugal action), whereupon it is returned to the circulation.

'l have found that ferric hydrate suspended in a solution of sulphate of iron is a good material for my purpose. llt may be used in any suitable washing apparatus -for washing the crude gas and then ybe passed into a tower which it descends, meeting air passing in the opposite direction; and from this tower it may be returned to the washer. Tn '-the. accompanying diagramsrepreilo -senting vertical sections of apparatus 1 shows anapparatus for carrying out the invention when circulation of the revivifying gas is not adopted. Fig. 2 shows a reaction towerV suitable for use when circulation of the revivifying .gas is employed. Fig. 3 shows a reaction tower suitable for use when the revivifying gas is caused to travel slowly through the tower. Fig. 4

shows a lnodiication.l

Referring to Fig. 1, the cold and clean gas to be purified frolnHzS is passed at a into the absorption tower A which it leaves at b, having passed through a filter c forremoving spray carried forward by the gas. rlihe suspension enters at d and flows, over distributing cones and discs of well-known type, to the bottom of the tower which itl leaves at e. Pump n' forwards it to the top of the revivifying tower B which it enters at This tower may be packed in any suitable known manner or may be designed likevessel A; at top it has a ilter z' for removing spray and at bottom receives air from a blower f.

The pipe I through which the suspension flows into-thecollecting tankat theI bottom point d of .tower A..4 A portion -of the suspension is continuously or periodically removed to'the centrifugal separator m by means of a pipe from the extreme bottom of l. the tower B, controlled by valve Z, or by y the sump means of a pipe from the discharge side of pump o, controlled by the valve p, or by means of both such pipes. In this manner the vsuspension may be withdrawn from the upper or .the lower part, or vboth parts, of at the bottom of tower B at will. The sulphur having been separated, the oxide material and the solution are returned to the HZS absorbing system.

A suitable suspension for use in such an apparatus consists of-a solution of ferrous sulphate containing 5 to 20 grams FeSO4-7H2() Y per litre, in which are suspended 10-40 grams of precipitated hydrated iron oxide per litre;

In Fi .'2 the reaction-tower q is fed with the sulp ided suspension through a iper,

the'suspension being returned to t e sulphiding vessel by pump s which withdraws it from the bottom of the tower. The pump t' draws air from thetower by ipe u and returns it to the tower by pipe lo. n the pipe u is a valve u1 placed between two branch pipes controlled by valves u2 and usvrespectively. By closing valves u2 and ua and opening valve u, the. gases in the tower will be circulated' in a closed cycle. By closing valve u1 and opening valves u2 and a3, fresh air will be drawn in at ua and foul air from the tower expelled at u2. By adjusting the three valves u1, u2 and us there may be a small currentof fresh air admitted at us .and a/corresponding current of foul air expelled at-u2.

In Fig. 3 the reaction tower g is suitably packed and into-it the supply of revivifying air is drawn by a chimney w so that a fan is not necessary. In this case the'revivifying gas is not circulated but is drawn in at the top ofthe tower through pipe a: at such a slow rate controlled by adjusting valve y, that the gases escaping by chimney 'w are suitably exhausted of available oxygen as aforesaid. As before, the suspension enters the tower at 1 and is removed by pump s.

If necessary any suitable means for improv-f ing the draught in chimney lw may be adopted, and-the -tendency of the `infiowing suspen sion to draw air through-'pipe may be relied upon to aid the process. The last named eifectmay be enhanced by `constructin-g the suspension delivery pipe r, in the manner shown in Fig. 4, within the air inlet pipe so as'. to cause. an injector action.

Having thus describedthe natureof the said invention, and the best means I know of carrying the same into practical effect, I claim i i 1. In a process of removing sulphur from gases by'means of a suspension of solid oxidizing agent, circulating the suspension in a distributed .conditionl in al closed path through one part of which vthe gas is continuously 4passed while into another part free oxygen is ,admittedat such a slow rate that 4the partial pressure of the available oxygen in the atmosphere in this part is reduced t0 that below, which revivification proceeds at an uneconomical rate.

2. In a process of removing sulphur from i gases by means of a suspension of solid oxi' dizing agent, circulating a suspension of hydrated ferrie oxide in a solution of ferrous sulphate in a distributed condition in a closed path through one art ofwhich the gas is continuously passe while in another part the suspension meets free oxygen.

In testimony whereof I have signed my name to this specication.

' NIELS E. RAMBUSH. 

